Bonded connection

Hello i have a balance 20x it has one sim card 100/20 down/up and a wired connection 300/24

How do i configure the 20x to use both at the same time for 400/44 ?

by default, when there are multiple active healthy wans the 20x will load balance sessions across them. So if you run speedtests from multiple connected devices and add up the results you will see somewhere approaching the total of your available bandwidth.

You can try speedfusion cloud if you would like to test speedfusion bonding. The maximum throughput you should should expect in this case is 100Mbps as that is the SpeedFusion / PepVPN bandwidth limit for the Balance 20x.